Pharmacological activation of WNT by lithium reduces radioresistance in medulloblastoma with mutant TP53. Since lithium is known to activate WNT signaling via inhibition of GSK3β, we examined whether pharmacological intervention could mimic the radiosensitivity observed in the WNT group and sensitize TP53 mutant cells to radiation. The gene discussed is GSK3B; the disease is medulloblastoma.